Computational and experimental investigation of chamber design and combustion process interaction in a spark ignition engine

[摘要] ENGLISH ABSTRACT:The automotive industry in South Africa is expanding as a result of pressure on theworld economy that forces vehicle manufacturers to outsouree work to developingcountries. In order to add value to automotive engine development, the capability toperform state-of-the-art engineering must be developed in this country. Threedimensionalfluid flow simulation is one such area and is being developed in this studyin order to enhance the ability to develop combustion systems. Another capability beingdeveloped at the University of Stellenbosch is the simulation of valve train dynamics.It was realised that there is a lack of research results of in-cylinder flow characteristicsand how they influence combustion chamber processes. This project focuses on theinvestigation of two different combustion chamber geometries and how they influencethe flow and combustion processes in two different combustion chambers. The aim is togain a better understanding of combustion chamber flow as an indirect result fromcomparing the flow in two fundamentally different engines under similar operatingconditions. The difference in the engines is that one was developed for reduced exhaustgas emissions while the other was developed to achieve high performance. Thenumerical simulation capability is developed in the process of achieving this goal.To achieve the above-mentioned aim, a literature study was performed on the differentcombustion chamber flow characteristics and how they are influenced by differentconfigurations. An experimental method of measuring combustion characteristics isstudied in order to establish the ability to perform the latter. Theory of numerical flowsimulation is also studied with this same goal in mind. Experimental testing isperformed and combustion analysis is done on the results. In conjunction to theexperimental work, numerical flow simulations are performed on the two differentcombustion chambers.The results from experimental testing and numerical simulations have shown thatobstructions in the flow into the combustion chamber, together with a port configurationthat cause flow around the longitudinal axis of the cylinder, increases the rate at whichfuel burns in the combustion chamber and thereby reduce the production of toxicemissions from the engine. The study also proved that reducing resistance to flowincreases the amount of air that is breathed by the engine and thereby results in increasedtorque generation.Through this study, opportunities for further research are identified. The results of thestudy can be used when new combustion systems are developed, especially in the lightof ongoing tightening of emission regulations. The contribution to numerical flowsimulation capabilities developed in this study add value to the ability to develop newcombustion systems in the future, especially when complimented by some of the furtherresearch topics identified.

[发布机构] Stellenbosch University